import java.util.Scanner;

public class Test1 {
    // 计算组合数 C(n, m)
    public static double combination(int n, int m) {
        if (m > n) return 0;
        double res = 1.0;
        for (int i = 1; i <= m; i++) {
            res *= (n - i + 1);
            res /= i;
        }
        return res;
    }

    public static void main(String[] args) {
        Scanner in = new Scanner(System.in);
        int n = in.nextInt();
        int m = in.nextInt();

        double pR = 0.8;
        double pOther = 0.2;

        double result = combination(n, m) * Math.pow(pR, m) * Math.pow(pOther, n - m);

        System.out.printf("%.4f\n", result);
    }
}
